Device for forming sheet metal joints and seams

ABSTRACT

A rotary hammer device for working sheet metal, particularly for closing sheet metal joints of the type commonly known as &#39;&#39;&#39;&#39;Pittsburgh Lock,&#39;&#39;&#39;&#39; wherein the hammer is reversible and is operable from both sides, so as to be movable in either longitudinal direction along the seam or joint.

United States Patent [151 3,638,596

Kemp 1 Feb. 1, 1972 [54] DEVICE FOR FORMING SHEET METAL [56] ReferencesCited JOINTS AND SEAMS UNITED STATES PATENTS Inventor: Joe R Kemp, 204West Dallas Road, 3,l88,729 6/1965 Pogue, Jr. et al. ..29/243.ssGrapevine,Tex. 3,195,492 7/1965 Erickson ..l l3/54 [22] Filed: June 1970Primary ExaminerRichard J. Herbst [2]] App]. 44 320 Attorney-E. HastingsAckley [57] ABSTRACT 52] us. Cl ..113/s4, 72/76 A rotary hammer devicefor working Sheet metal, particularly [5]] Int. Cl ..B2ld 3l/06 forclosing sheet metal joints of the type commonly known as Field of Search24353 Pittsburgh Lock," wherein the hammer is reversible and is operablefrom both sides, so as to be movable in either longitudinal directionalong the seam or joint.

10 Claims, 9 Drawing Figures PMENTED m1 m2 3.638.596

INVENTOR. Joe H. Kemp ATTORNEY DEVICE FOR FORMING SHEET METAL JOINTS ANDSEAMS OBJECTS AND SUMMARY OF THE INVENTION This invention relates tometalworking devices, more particularly to a power hammer-type deviceadapted for use with a rotary power tool, such as a drill, rotarywrench, sander or the like, for bending sheet metal without scuffing orotherwise damaging the surface of the sheet metal, and withoutdistorting or bending the metal other than to form the desired closureof the joint and provide a flat seam.

It is, therefore, one object of the device to provide a metalworkingtool of the character set forth for bending sheet metal seams and jointsadapted for use at a point remote from the metalworking shop.

A particular object of the invention is to provide a sheetmetal-workingdevice which is simple and economical to manufacture and use, and whichis of rigid and durable construction, which is adapted to be operatedeasily and effi-,

ciently on various gauges of sheet metal for bending the same, andparticularly for closing and bending a metal joint such as a PittsburghLock without damaging the metal.

It is an important object of the invention to provide a rotary hammer ofthe character described which has a pair of working surfaces, one oneach side of a discuslike body, the sides being reversible in use so asto be movable in either direction along the seam to fold or bend themetal as desired at either end of the joint.

It is still another object of the invention to provide a device of thecharacter described which may be carried to a remote job for use withrotary power tools such as electric drills, sanders, grinders, orsimilar portable hand-held power units. The device is likewise adaptedto use with rotary air or pneumatictype power units.

Still another object of the invention is to provide an improved hammermember of the character described having means for preventing vibrationof the peripheral edge portions of the hammer member under heavystresses and impacts.

A still further object of the invention is to provide a rotary hammerfor forming sheet metal made in substantially the form of a discus,having metalworking surfaces on the marginal portions of opposite sidesthereof, and formed by abutting the edges of a pair of saucerlikesections with their concave sides facing inwardly and welding orotherwise similarly rigidly joining the abutting edges to provide theunitary two-faced discus-shaped tool.

Additional objects and advantages of the invention will be readilyapparent from the reading of the following description of a deviceconstructed in accordance with the invention, and reference to theaccompanying drawings thereof, wherein:

FIG. 1 is a fragmentary isometric view of a hammer member made inaccordance with the invention operated by a rotary power tool andshowing the hammer member being moved along a sheet metal joint to closethe joint;

FIG. 2 is a view similar to FIG. 1 from another angle, showing thehammer member being used to completely fold down the bend and tocomplete the joint;

FIG. 3 is an enlarged plan view of the hammer member of FIG. 1;

FIG. 4 is a still further enlarged cross-sectional view taken on theline 4-4 ofFIG. 3;

FIG. 5 is an enlarged fragmentary view of the work surface portion ofone of the sections of the hammer member;

FIG. 6 is a fragmentary sectional view taken on the line 6- 6 of FIG. 5.

FIG. 7 is a fragmentary cross-sectional view, similar to FIG. 4, of amodified form of hammer member;

FIG. 8 is a view similar to FIG. 7 of a further modified form of hammermember; and,

FIG. 9 is a fragmentary view of still another modified form of thedevice.

BACKGROUND, CONSTRUCTION AND OPERATION OF PREFERRED EMBODIMENT Varioustypes of machines have been used in the past for forming sheet metal toclose joints such as the Pittsburgh Lock, but most such machines havenot been portable and have not provided for use in forming the sheetmetal to close the joint at the installation point, or point of use, ofthe sheet metal-construction. The joint of the type described is widelyused in the sheet metal industry to fasten opposite edges of sheets ofsheet metal together to form a duct corner, or to fasten two edges ofdifferent sheet metal together for other structures. The sheets to bejoined each have their edge portion prefabricated in a particularmanner, one sheet 10 (FIGS. 1 and 2) having its edge portion bent at anangle to form a flange 11, and this sheet is called the angled sheet.The other sheet of metal 12, called the replaited sheet, has its edgeportion folded back on itself to form a flat S-type fold having an innerportion 13, a middle portion 14 and an outer portion 15. The middle andouter folds l4 and 15 are spaced slightly from each other to form anoutwardly facing channel or groove 16 which is adapted to receive theflange ll of the angled sheet. The outer fold 15 has its edge portionprojecting beyond the folds 13 and 14 to form a bendable flange portion17, commonly called the outstanding edge. In forming the PittsburghLock," the flange 11 of the angled sheet 10 is inserted fully into thechannel 16 of the replaited sheet, then the projecting flange oroutstanding edge 17 of the replaited sheet 12 is folded flat along theexposed surface of the angled sheet 10 at the bend between the sheet 10and the flange 11 along the seam line 18, so that the bent projectingflange or outstanding edge 17 lies flat against the angled sheet 10 toclose the joint lock and hold the two sheets firmly together.

Obviously, the operation of bending the flange or edge 17 by hand, or byhammer or other tools, is a time consuming and inefficient operation,and may result in damage to the sheet metal flange portion, or providean insecure and irregular lock joint, or both. Reciprocating hammershave the same objection, in that they may provide an irregular joint, ordamage the material forming the flange. Other types of devices which areadapted to ride along the seam of the joint and press the outstandingedge into its locked position are difficult to operate, are complex andexpensive and ordinarily can be used with only relatively limited rangesof metal thickness. Also, many of these machines are not portable or arenot adequately sturdy to withstand continued usage, and requireconsiderable maintenance. In addition, in many of the machinesheretofore in use, the machine will not operate to close the joint at aninternal angle, where the outstanding flange edge must be closedadjacent a projecting portion of the sheet metal structure. Heretofore,it has been necessary to complete the closing of the joint by hand orhandtools on the job.

Referring to the accompanying drawings, a standard rotary power tool 20,such as an electric or pneumatic drill, sander, or other type portablepower device, having a nose portion 21 with a rotary shaft 22 projectingtherefrom is provided with the discuslike hammer member 25 of thisinvention. In the preferred form, the hammer member 25 has a centralsubstantially planar section 26 and an annular convex work surface 27 onits outer peripheral portion, one each of the two opposite side sections28 and 29 thereof. A plurality of identical hammer elements 30a, 30b,30c and 30d are formed on and spaced uniformly angularly about theexposed convex work surfaces to the two sides 28 and 29 of the hammermember, As shown in FIG. 4, the discuslike body of the hammer member isformed by the two identical dishlike or dish-shaped sections or halves28 and 29 each having a central planar disc portion 26 and an annularconcave-convex portion 32 on its outer circumferential or peripheralsection, which provides the annular convex work surfaces 27 on each sideof the hammer member having the plurality of hammer elements thereon.The two dishlike sections 28 and 29 are placed with their concaveperipheral portions 32 facing each other and are joined, as by weldingat 33, around the outer circumferential edges of the sections to jointhe sections into a unit. Also, the hammer elements 30a and 30b of thefirst section 28 are disposed at substantially right angles with respectto the center of the hammer member to the position in which the hammerelements 300 and 30d of the other section 29 are disposed. Thus, as isclearly shown in FIG. 3, the hammer elements 30a and 30b of the section28 lie on a diameter which is disposed at right angles to the diameterof the section 29 in which the hammer elements 300 and 30d are disposed.The impact sections of the hammer member adjacent the hammer elementsare therefore spaced from each other on opposite sides of the hammermember, so the chance of cracking or failure in stress of any kind atthe hammer elements or the hammer impact sections of the body sectionsis reduced, since each body section is welded or otherwise secured tothe opposite body section in a position in which the hammer elementsthereon are located at points uniformly spaced from the hammer elementson the opposite body section.

As shown in FIGS. 5 and 6, the preferred form of the device is made bydie forming or pressing a sheet of metal to provide identical sections,such as the sections 28 and 29, each having the concavo-convex worksurface portion 32 formed with the hammer elements made by deforming themetal to provide the projecting hammer element 30d in the shape ofsubstantially a teardrop or conical bulbar projection protruding fromthe convex work surface 27 of the hammer member section 29. Theprotruding portion 300! extends completely to the marginal edge of theconcave-convex portion of the hammer section, the hammer element beingformed by die shaping the same to project as shown in FlGS. 5 and 6.When the body sections 28 and 29 are joined in the manner shown in FIGS.1 through 4, by welding along the peripheral edges of the sections as at33, the open outer ends of the conical bulbar or teardrop-shaped hammerelements are closed by the weld and joined rigidly to the circularmarginal edge portion of the opposite body section, and so the hammerelements are reinforced and strengthened to withstand substantialhammering.

The hammer member 25, is therefore, substantially hollow, having theannular concavo-convex portions 32 thereof providing a pair of opposedconvex annular work surfaces 27 which carry the uniformly spaced hammerelements. The weight of the tool is therefore reduced, while thestrength of the tool is increased by joining the two sections. Also, thecentral planar disc portions 26 of the body sections 28 and 29 arespaced from each other to provide a more stable means for supporting abushing 22a for clamping the hammer readily on the shaft 22 of the powerunit 20.

The device shown in FIGS. 1 through 4 is completely reversible inconstruction and operation. Either section 28 or 29 of the hammer member25 may be secured adjacent the outer end of the shaft, and the devicewill be usable regardless of which section is exposed opposite the powerunit. Furthermore, by providing the two identical opposed side sections,the hammer member may be reversed and the side nearest the power unitutilized as a hammer to deform or bend the flange, and so provide forclosing a joint up to a projecting portion of the metalwork forming aninternal angie between the portion on which the joint is being closedand an adjacent section. The hammer member is therefore reversible andmay be used with either surface adjacent the power unit, and the othersurface spaced from the power unit.

As will be seen, in FIGS. 1 and 2, the power unit or rotary tool is sopositioned in use that the hammer is disposed at an angle to the planeof the upper surface of the angled sheet 10 and at an angle to theprojecting flange or outstanding edge 17 of the replaited sheet. As thehammer member is rotated in a clockwise direction, as shown by the arrowin FIG. 1. the hammer elements c and 30d on the body section 29 willrepeatedly and rapidly engage the upstanding flange portion 17 and bendthe same toward the angled plate 10 by repeated blows against theupstanding flange portion as the device is moved in the direction of thearrow in FIG. I from the closed portion of the joint toward theupstanding unclosed portion. Since the hammer member is rotated at arelatively high speed, a large number of small hammer impacts or blowsare transmitted by the hammer elements 300 and 30d to the sheet metalflange to form the same without damaging it and to provide a uniformsmooth joint. To completely close the joint, the hammer and power unitare turned to a position substantially at right angles to the angledplate, to completely fold or bend the flange 17 flat against the angledplate, as shown in FIG. 2.

Should it be necessary, while forming the fold or bend in the sheetmetal adjacent a structure extending upwardly at right angles to theangled plate 10 at the open end of the joint, when the leading edge ofthe hammer member would engage the upwardly extending structure beforethe hammer elements 300 and 30d can complete bending the flange l7completely to such structure, it is apparent that the power unit and thehammer member 25 may be reversed in position to engage the hammerelements 30a and 30b on the body section 28 nearest the hammer with theoutstanding flange 17 to bend the flange downwardly completely up to theprojecting structure without the necessity of hand hammering or bendingthe flange. Thus, the two sections 28 and 29 forming the two opposedconvex shapes of work surface portions 27 of the hammer member providefor hammering close to an angle joint where the flange portion 17 mustbe bent adjacent another section or sheet which is disposed at an angleto the surface of the angled sheet 10. Further, the two work surfaces 27on opposite side sections 28 and 29 of the body of the hammer memberpermit the hammer to be used closely adjacent such angle joint at eitherend of the section on which the joint is being closed.

Obviously, also, the curved convex work surface portions of the hammermember provide, by controlling the angle at which the hammer member isheld with respect to the flange portion 17, control of the forceimparted to the flange portion of the sheet metal by the hammerelements. Furthermore, since the hammer member is formed of two bodysections having their outer marginal edges joined, it will be seen thatthe opposed concavo-convex portions 32 of the hammer sections stiffenand reinforce the outer edge portions of the hammer member, particularlyadjacent the hammer elements and so provide a more rigid and asatisfactory hammer member in which the hammer elements shaped in themetal from which the body sections are made is not likely to failadjacent the hammer elements. Likewise, the hollow body member providesa lighter weight hammer member, and still a strong rigid member.

As is clearly shown in FIGS. 1 through 4, the hammer elements are formedin substantially teardrop shape, or a substantiaily conical bulbarshape, extending from the central portion of the convex surfaces 27toward the outer peripheral edge thereof. The reduced or smallerportions are disposed medially inwardly along the diameter of thesections toward the center of the hammer and increase in size andthickness outwardly from that medial portion toward the circumferentialedge of the section. This shape provides for variation in the hammerblow which can be effected by the hammer member by varying the angle ofattack on the sheet metal flange portion 11 struck by the hammerelements, a larger and heavier blow being struck by the greaterprojecting outer portions than is the case when the sheet metal isstruck by the lesser inner projecting portion. The surface of each ofthe hammer elements 30a, 30b, 30c and SM is smoothly curved to preventdamaging the sheet metal, and may be formed of a die pressed portion, asshown in FIGS. 3 through 7 of the mate rial of which the body sectionsare formed, or may be formed by welding or building the same up of ahardened material, such as tungsten carbide or the like, which willwithstand wear and heavy impact of usage, as shown in FIG. 9.

The circular or disc portion 26 of the hammer member is provided with anaperture 40 which extends centrally through both central disc portions26 of the body sections 28 and 29 by means of which the hammer membermay be attached to the shaft 22 of the power unit 20 in the usual mannerby clamping the hammer unit on the shaft with a bolt 41 and a clampingwasher 42 to the shaft 22 of the power unit to securely clamp the hammermember on the shaft for rotation thereby. If desired a suitable key slotmay be provided, but is not necessa- The central disclike portion 26 isplanar, and is, as shown in FIG. 4, disposed inwardly toward theadjacent section in planes lying between the projecting convex portions27 of the body sections 28 and 29, which prevents the central portion 26of the hammer member on either side from contacting the sheet metalbeing formed.

While two hammer elements have been shown as provided on the convex worksurface of each body section, it is obvious that any other number ofsuch hammer elements may be formed on the work surfaces, so long as theyare equal in number and uniformly spaced around the convex hammer worksurfaces on eachside section, so that a uniform hammering action will beeffected as the hammer member is rotated.

It is preferable that the hammer elements be forged or formed as anintegral part of the hammer sections 28 and'29 as shown in FIGS. 3through 7, so that the hammer elements project from the convex surface.This produces a more economical structure in manufacture, and, when thetwo body sections are welded together in the manner illustrated in FIGS.3 and 4 into a unitary body member, the strength of the hammer elementsis the same as if the hammer elements had been deposited on the convexsurface by welding or otherwise.

MODIFIED FORMS The form of the hammer shown in FIGS. 3 through 6 ispreferable. However, the hammer may be made with only one workingsurface, reinforced as shown in FIGS. 7 through 9.

As shown in FIG. 7, one body section 129, having the hammer elements 130formed thereon, is welded to a plate or disc 150 of the samecircumferential sizeas the body section and having a central aperture151 therein aligned with the aperture 140in the body section 129. Theweld 152 joining the disc 150 to the bodysection 129 provides increasedrigidity and strength to the dishlike body section 129 and preventsdamage to the working surface portion 127 of the body section adjacentthe hammer elements 130 in much the same manner as in the formillustrated in FIGS. 3 and 4, though without the convex opposed worksurfaces provided by the body member formed of the two identical opposedbody sections as shown in FIG. 4. Other construction of the body section129 is identical to that of the body section 29 shown in FIGS. 3 through6.

Also, if desired, as shown in FIG. 8, the single body section 129a maybe provided with a rigidifying or reinforcing member 160 which is thesame diameter and welded at its outer edges 162 to the body member 129a,but has its central disc portion 163 having an aperture 161 therethroughpressed downwardly in a frustoconical shape toward the central discportion 126 of the body section 129a to lie adjacent and in engagementwith the disc portion of said body section 129a. The marginal edges ofthe reinforcing member 160 are welded to the edges of the body section129a, and, if desired, the central disc portion 163 of the reinforcingmember may be spotwelded to the central disc portion 126a of the bodysection 129.

A further modification of the hammer member or device is shown in FIG. 9wherein the reinforcing member 170 is in the form of an annulus shapedas a truncated cone, having its outer edge portion 172 welded to theouter edge of the body section 229 and having its inner truncatedportion 173 welded as at 175 to the central disc portion 226 of the bodysection 229 to provide means rigidifying or reinforcing theconcaveconvex work section 227 of the body member.

As shown in FIG. 9 the hammer elements 330 may be formed on the hammersection 229 by welding deposition to project from the work surface 227if desired. Also, the hammer side section 229 may be reinforced in thesame manner as in FIGS. 6 through 8.

These devices function in the same manner as the device of FIGS. 3 and4'and provide a reinforced convex work surface in a rigidified andstrengthened hammer member for forming metal bends.

From the foregoing, it is believed readily apparent that an economical,portable, forming tool or power hammer member has been disclosed whichis particularly adapted for use in forming sheet metal, moreparticularly for closing sheet metal joints such as the PittsburghLock." It will also be apparent that the device is portable, economicalto manufacture, easy to use, adapted for carrying to a remote job, andusable with standard power tool equipment such as drills, grinders,sanders or the like having a rotatable shaft. It will also be seenthatan improved hammer member has been provided which is strengthenedalong its work surface to rigidify the work portion thereof and supportthe work ,surface adjacent the hammer elements. It is also particularlyapparent that, in the preferred form, a hammer member has been providedwhich is reversible and has two opposed work surfaces, either of whichmay be used without reversing the hammer member on the rotating powerunit.

The foregoing description of the invention is explanatory only, andchanges in the details of the construction illustrated may be made bythose skilled in the art, within the scope of the appended claims,without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent l. Ametal-forming tool adapted to be used to fold sheet metal flanges toclose metal joints, including: a body member having a centraldisc-shaped body portion having an outer annular convex work surfaceportion; a plurality of projecting hammer elements disposed in uniformlyspaced positions are moved in a circular path to engage and deform orbend a portion of a sheet of sheet metal to fold said portion to adesired position; said body member being formed of a pair of opposedsubstantially identical dishlike body sections joined at their marginaledges and each having said annular convex work surface portion with saidhammer elements formed thereon disposed on opposite sides of said bodymember with the hammer elements of each dishlike body section projectingtherefrom opposite the hammer elements on the section forming theopposite side of the body member.

2. A metal-shaping hammer means including: a body member formed of apair of substantially identical dishlike body sections joined togetheralong their marginal edge portions to form a unitary hollow body member;each dishlike body section having an annular concavo-convex peripheralwork surface portion and a disc-shaped central support portion, saidcentral portion being disposed in a plane spaced from the plane of theconvex surface of said peripheral work surface portion; a plurality ofprojecting hammer elements disposed to project from the convex worksurface of each of said body sections, said projecting hammer elementsbeing disposed at uniformly spaced positions about the center of saidbody and projecting from the outer convex portion of the annularperipheral edge work surface portion thereof, said hammer elements beingsubstantially teardrop in configuration along the surface of the convexperipheral work surface portion of the body member, with the largerbulbar portion of the teardrop shape disposed outwardly from the centerof the body section to the edge thereof; said body sections being joinedto position the teardroplike hammer elements at unifomily spaced pointsaround the circumference of the outer marginal edge portion of the bodymember, so that hammer elements on one body section are spaced uniformlybetween the hammer elements on the opposite body section.

3. A hammer means of the character set forth in claim 2 wherein thehammer element on each body section is formed by forging the sameintegral with the body section.

4. A device of the character set forth in claim 2 wherein the bodymember and the hammer elements thereon are formed by die shaping thesame to provide the body member with the annular convex peripheral worksurface portion.

5. A device of the character set forth in claim 2 wherein a centralaperture is provided in the disclike central portions of the bodysections to provide means for securing said body member to the rotatableshaft of a rotary power unit for rotating the same.

6. A device of the character set forth in claim 1 wherein the hammerelements of each body section are formed of a body of hard materialdeposited on the convex surface of the annular outer work surfaceportion of the body section and having a shape flaring outwardly fromthe inner portion of the hammer element toward the outer edge portionthereof and projecting to an increased degree from said convex worksurface from the inner portion of the work surface toward the outermarginal edge thereof.

7. A metal-forming tool adapted to be used to form sheet metal flangesto close metal joints including: a body member formed of twosubstantially identical opposed dishlike body sections joined alongtheir edges, each said body section having a planar disk-shaped centralportion and an annular dishlike concavo-convex outer work surfaceportion; a plurality of projecting hammer elements disposed in uniformlyspaced positions about the convex surface of the work surface portion ofthe body section and each projecting unifonnly from said convex surfacein exposed striking position; means formed centrally of the disc-shapedcentral portion of the body section for mounting the body member on therotatable shaft of a rotary power tool for rotation thereby whereby theplurality of exposed projecting hammer elements on the convex worksurface portions of the opposed body sections are moved in a circularpath to be used to engage and deform or bend a portion of a sheet ofsheet metal to fold said portion to a desired position.

8. A metal-shaping hammer means including: a discuslike body memberhaving an annular convex outer edge work surface portion on each sidethereon and a central planar disclike portion disposed in a plane spacedfrom and within the planes of the projecting convex work surfaceportions; said planar disclike portion having a central aperture thereinfor use in mounting the body member on a rotary shaft of a power unit tobe driven thereby; said body member being formed of a pair of opposeddishlike body sections of substantially identical configuration havingtheir concave portions facing inwardly toward each other and joinedrigidly along their circumferential edge portions into a unit to providethe body member; each of said body sections having a plurality ofprojecting hammer elements disposed to project from the convex surfaceof said concave-convex annular work surface portion of said bodysection, said projecting hammer elements being disposed at positionsuniformly spaced about the center of said disclike central portion andprojecting from the outer convex portion of the annular outer worksurface portion, said hammer elements being flared outwardly in shapealong the convex surface of the convex work surface portion of the bodysection with the larger portion of the flared shape disposed outwardlyfrom the center of the body and extending to the outer edge of said bodysection.

9. A metal-shaping hammer means of the character set forth in claim 8wherein each of said sections is formed by die shaping the same to formthe concavo-convex outer annular work surface section and to shape thehammer elements to project from the convex surface of said annular worksurface section.

10. A hammer of the character set forth in claim 8 wherein the hammerelements on the annular convex work surface portions of each section arespaced uniformly circumferentially about the outer edge of the bodysections to dispose said hammer elements on one body section spaceduniformly between the adjacent oppositely projecting hammer elements ofthe opposite work surface of the opposite body section.

1. A metal-forming tool adapted to be used to fold sheet metal flanges to close metal joints, including: a body member having a central disc-shaped body portion having an outer annular convex work surface portion; a plurality of projecting hammer elements disposed in uniformly spaced positions about the convex work surface portion of the body member and each projecting from said convex surface in exposed striking position; means formed centrally of the disc-shaped body portion of the body member for mounting the same on a rotatable shaft of a rotary power tool for rotation thereby, whereby the plurality of exposed projecting hammer elements are moved in a circular path to engage and deform or bend a portion of a sheet of sheet metal to fold said portion to a desired position; said body member being formed of a pair of opposed substantially identical dishlike body sections joined at their marginal edges and each having said annular convex work surface portion With said hammer elements formed thereon disposed on opposite sides of said body member with the hammer elements of each dishlike body section projecting therefrom opposite the hammer elements on the section forming the opposite side of the body member.
 2. A metal-shaping hammer means including: a body member formed of a pair of substantially identical dishlike body sections joined together along their marginal edge portions to form a unitary hollow body member; each dishlike body section having an annular concavo-convex peripheral work surface portion and a disc-shaped central support portion, said central portion being disposed in a plane spaced from the plane of the convex surface of said peripheral work surface portion; a plurality of projecting hammer elements disposed to project from the convex work surface of each of said body sections, said projecting hammer elements being disposed at uniformly spaced positions about the center of said body and projecting from the outer convex portion of the annular peripheral edge work surface portion thereof, said hammer elements being substantially teardrop in configuration along the surface of the convex peripheral work surface portion of the body member, with the larger bulbar portion of the teardrop shape disposed outwardly from the center of the body section to the edge thereof; said body sections being joined to position the teardroplike hammer elements at uniformly spaced points around the circumference of the outer marginal edge portion of the body member, so that hammer elements on one body section are spaced uniformly between the hammer elements on the opposite body section.
 3. A hammer means of the character set forth in claim 2 wherein the hammer element on each body section is formed by forging the same integral with the body section.
 4. A device of the character set forth in claim 2 wherein the body member and the hammer elements thereon are formed by die shaping the same to provide the body member with the annular convex peripheral work surface portion.
 5. A device of the character set forth in claim 2 wherein a central aperture is provided in the disclike central portions of the body sections to provide means for securing said body member to the rotatable shaft of a rotary power unit for rotating the same.
 6. A device of the character set forth in claim 1 wherein the hammer elements of each body section are formed of a body of hard material deposited on the convex surface of the annular outer work surface portion of the body section and having a shape flaring outwardly from the inner portion of the hammer element toward the outer edge portion thereof and projecting to an increased degree from said convex work surface from the inner portion of the work surface toward the outer marginal edge thereof.
 7. A metal-forming tool adapted to be used to form sheet metal flanges to close metal joints including: a body member formed of two substantially identical opposed dishlike body sections joined along their edges, each said body section having a planar disk-shaped central portion and an annular dishlike concavo-convex outer work surface portion; a plurality of projecting hammer elements disposed in uniformly spaced positions about the convex surface of the work surface portion of the body section and each projecting uniformly from said convex surface in exposed striking position; means formed centrally of the disc-shaped central portion of the body section for mounting the body member on the rotatable shaft of a rotary power tool for rotation thereby whereby the plurality of exposed projecting hammer elements on the convex work surface portions of the opposed body sections are moved in a circular path to be used to engage and deform or bend a portion of a sheet of sheet metal to fold said portion to a desired position.
 8. A metal-shaping hammer means including: a discuslike body member having an annular convex outer edge work surface portion on each side thereon and a central planar disclike portion diSposed in a plane spaced from and within the planes of the projecting convex work surface portions; said planar disclike portion having a central aperture therein for use in mounting the body member on a rotary shaft of a power unit to be driven thereby; said body member being formed of a pair of opposed dishlike body sections of substantially identical configuration having their concave portions facing inwardly toward each other and joined rigidly along their circumferential edge portions into a unit to provide the body member; each of said body sections having a plurality of projecting hammer elements disposed to project from the convex surface of said concavo-convex annular work surface portion of said body section, said projecting hammer elements being disposed at positions uniformly spaced about the center of said disclike central portion and projecting from the outer convex portion of the annular outer work surface portion, said hammer elements being flared outwardly in shape along the convex surface of the convex work surface portion of the body section with the larger portion of the flared shape disposed outwardly from the center of the body and extending to the outer edge of said body section.
 9. A metal-shaping hammer means of the character set forth in claim 8 wherein each of said sections is formed by die shaping the same to form the concavo-convex outer annular work surface section and to shape the hammer elements to project from the convex surface of said annular work surface section.
 10. A hammer of the character set forth in claim 8 wherein the hammer elements on the annular convex work surface portions of each section are spaced uniformly circumferentially about the outer edge of the body sections to dispose said hammer elements on one body section spaced uniformly between the adjacent oppositely projecting hammer elements of the opposite work surface of the opposite body section. 